Gas generating composition

ABSTRACT

The present invention provides a gas generating composition including a basic magnesium carbonate in addition to a fuel and an oxidizing agent, the content of the basic magnesium carbonate being less than 20 mass %.

This nonprovisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2006-343707 filed in Japan on 21 Dec. 2006 which is incorporated by reference.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to a gas generating composition that can be used in a gas generator for an air bag apparatus.

2. Description of Related Arts

A gas generating agent including guanidine nitrate and basic copper nitrate is known to be used in order to purify (to decrease the concentration of nitrogen oxides, ammonia, and carbon monoxide) a gas generated from a gas generator. In addition, 5-aminotetrazole is known to be used as a fuel and basic copper nitrate as an oxidizing agent.

JP-A No. 2006-76849 discloses a gas generating composition including a tetrazole compound, a guanidine compound, a nitrate, a perchlorate, and a basic carbonate, wherein the content of the basic carbonate is more than 20 mass % but not more than 40 mass %.

Other related arts to the present invention may be JP-A No. 2002-12493, JP-A No. 2004-67424 or WO-A No. 03/16244.

SUMMARY OF INVENTION

The present invention provides a gas generating composition containing a basic magnesium carbonate in addition to a fuel and an oxidizing agent, the content of the basic magnesium carbonate being less than 20 mass %.

DETAILED DESCRIPTION OF INVENTION

The present invention provides a gas generating composition that can increase the purification degree of exhaust gas and is suitable for a gas generator of an air bag apparatus.

In other words, the present invention provides a gas generating composition containing a fuel and an oxidizing agent, characterized by further containing less than 20 mass % of a basic magnesium carbonate.

The present invention further provides the gas generating composition, wherein the content of the basic magnesium carbonate is preferably 18 mass % or less.

The present invention further provides the gas generating composition, wherein the oxidizing agent includes preferably basic copper nitrate.

The present invention further provides the gas generating composition, wherein the fuel is preferably selected from melamine, melamine cyanurate, guanidine nitrate, and nitroguanidine.

By using the gas generating composition in accordance with the present invention, it is possible to increase the purification degree of an exhaust gas.

EMBODIMENTS OF INVENTION

A nitrogen-containing compound that has been used in known gas-generating agents can be used as the fuel of the present invention, such as compounds described in JP-A No. 2002-12493, JP-A No. 2004-67424 and WO-A No. 03/16244. It is preferred to be at least one or two or more selected from melamine, melamine cyanurate, guanidine nitrate, and nitroguanidine.

The content of the fuel in the composition is preferably 10 to 55 mass %, more preferably 12 to 50 mass %, even more preferably 14 to 45 mass %.

An oxidizing agent that has been used in known gas-generating agents can be used as the oxidizing agent of the present invention, such as compounds described in JP-A No. 2002-12493, JP-A No. 2004-67424 and WO-A No. 03/16244. It is preferable at least one or two or more selected from basic copper nitrate, basic copper carbonate, potassium nitrate, sodium nitrate, strontium nitrate, potassium perchlorate, sodium perchlorate, and ammonium perchlorate.

The content of the oxidizing agent in the composition is preferably 30 to 85 mass %, more preferably 35 to 80 mass %, even more preferably 40 to 75 mass %.

In accordance with the present invention, basic magnesium carbonate is further contained in addition to the fuel and oxidizing agent. Basic magnesium carbonate changes into magnesium oxide during combustion. Magnesium oxide is a stable compound, does not function as an oxidizing agent as basic copper nitrate and basic copper carbonate, and is apparently a component that acts to purify the exhaust gas.

The content of basic magnesium carbonate in the composition is less than 20 mass %, preferably 18 mass % or less, even more preferably 15 mass % or less. The lower limit is preferably 2 mass % or more.

It is preferable that the content of basic magnesium carbonate in the composition ranges from 18 mass % to 2 mass %.

If necessary, the gas generating composition in accordance with the present invention can include a known binder. Examples of known binders include carragennan, pectin, arginine-carbomer, sodium alginate, propylene glycol alginate, xanthan gum, guar gum, gum arabic, cyclodextrin, sodium polyacrylate, carboxymethyl cellulose, carboxymethyl cellulose potassium salt, carboxymethyl cellulose sodium salt, carboxymethyl cellulose ammonium salt, cellulose acetate, cellulose acetate butyrate, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl ethyl cellulose, microcrystalline cellulose, polyacrylamides, amino-compounds of polyacrylamides, polyacryl hydrazide, copolymers of acrylamide and acrylic acid metal salt, copolymers of polyacrylamide and polyacrylic acid ester compound, polyvinyl alcohol, acrylic rubber, starch, silicone, and the like.

Among them, carboxymethyl cellulose sodium salt is preferred from the standpoint of increasing the degree of purification of an exhaust gas.

Examples of a preferable additive include, metal oxides such as iron oxide, zinc oxide, cobalt oxide, manganese oxide, molybdenum oxide, nickel oxide, bismuth oxide, silica or alumina; metal hydroxides such as cobalt hydroxide or iron hydroxide; cobalt carbonate, calcium carbonate; a composite compound of a metal oxide and a hydroxide, including Japanese acid clay, kaolin, talc, bentonite, diatomaceous earth or hydrotalcite; metal acid salts such as sodium silicate, mica molybdate, cobalt molybdate or ammonium molybdate; silicone, molybdenum disulfate, calcium stearate, silicon nitride, and silicon carbide.

The gas generating composition in accordance with the present invention can be molded into a desired shape, and can be obtained as a molded body in the form of a cylinder with a single hole, a cylinder with multiple holes, or a pellet.

The molded bodies can be manufactured by a method by which water or an organic solvent is added to, and mixed with the gas generating composition, followed by extrusion-molding (molded body in the form of a cylinder with a single hole or a cylinder with multiple holes) or a method by which the mixture is compression-molded by using a pelletizer (pellet-shaped molded body). Holes in the cylinder with a single hole or cylinder with multiple holes may pass through in the longitudinal direction or may be recesses without passing through.

The gas generating composition in accordance with the present invention or a molded body thereof can be applied to an airbag inflator for a driver side, an airbag inflator for a passenger side next to the driver, a side airbag inflator, an inflator for an inflatable curtain, an inflator for a knee bolster, an inflator for an inflatable seat belt, an inflator for a tubular system, and a pretensioner, mounted in various vehicles.

An inflator using gas generating composition of the present invention or a molded body thereof may be a pyrotechnic type in which gas is supplied only from the gas generating agent, or of a hybrid type in which gas is supplied from both the compressed gas such as argon and the gas generating agent.

Further, the gas generating composition in accordance with the present invention or a molded body thereof can be also used as an ignition agent called an enhancer agent (or a booster) or the like serving for transferring the energy of a detonator or a squib to the gas generating agent.

EXAMPLES Examples and Comparative Examples

Gas generating compositions composed of the components shown in Table 1 were manufactured. Gas concentrations were measured by the following method by using the gas generating compositions.

Measurement of Gas Concentration

The compositions of Examples and Comparative Examples (compositions in a powdered state prior to molding that were composed from the components shown in Table 1) were loaded into a mortar side of a predetermined die, removed therefrom after they had been compressed and held for 5 seconds under a pressure of 14.7 MPa with a hydraulic pump and molded to obtain a cylindrical strand having an outer diameter of 9.55 mm and a length of 12.70 mm. Drying was then performed for 16 hours at 110° C. An epoxy resin adhesive of a chemical reaction type “Bond Quick 30” manufactured by KONISHI CO., LTD. was coated on the side surface of the cylindrical molded body to obtain a sample that is ignited and combusted only from the end surfaces, without being ignited from the side surface (single-surface propagating combustion).

Then, the cylindrical strand (mass 2.00 g) was disposed inside a sealed cylinder made from SUS and having an internal capacity of 1 L, and the inside of the cylinder was pressurized to 7 MPa and stabilized at this pressure, while replacing the entire atmosphere in the cylinder with nitrogen. A predetermined current was then passed to nichrome wires that is in contact with the end surfaces of the strand, and the strand was ignited and combusted by the fusing energy thereof. After waiting for 60 seconds till the gas inside the cylinder became homogeneous, the open plug portion of the predetermined Teddler bag equipped with a plug was connected to a gas discharge portion of the cylinder, the combustion gas located inside the cylinder was sampled by transferring into the bag, and the concentrations of NO, NH₃, and CO were measured by Gastec detection tubes (No. 10 for detection of NO₂ and NO; No, 3L for detection of NH₃; No, 1L for detection of CO) by using a detector GV-100S manufactured by GASTEC CORPORATION.

TABLE 1 Composition of Gas generating composition (mass %) exhaust gas (ppm) Melamine BCN BCC BMC CMCNa NO NH₃ CO Example 1 16.32 73.86 0 5 5 62 90 120 Example 2 15.28 69.72 0 10 5 13 55 120 Example 3 14.24 65.76 0 15 5 10 26 100 Comparative Example 1 13.2 61.8 0 20 5 No ignition Comparative Example 2 16.82 73.18 5 0 5 120 85 140 Comparative Example 3 16.29 68.71 10 0 5 55 100 150 Comparative Example 4 15.75 64.25 15 0 5 18 65 170 Comparative Example 5 15.21 59.79 20 0 5 18 80 180 BCN: basic copper nitrate BCC: basic copper carbonate BMC: basic magnesium carbonate

The invention thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. 

1. A gas generating composition comprising a basic magnesium carbonate in addition to a fuel and an oxidizing agent, the content of the basic magnesium carbonate being less than 20 mass %.
 2. The gas generating composition according to claim 1, wherein the content of the basic magnesium carbonate is 18 mass % or less.
 3. The gas generating composition according to claim 1, wherein the oxidizing agent comprises basic copper nitrate.
 4. The gas generating composition according to any one of claims 1 to 3, wherein the fuel is selected from the group consisting of melamine, melamine cyanurate, guanidine nitrate and nitroguanidine. 